This invention relates generally to semiconductor manufacture and specifically to the handling of semiconductor components including packages, chip scale packages, BGA devices, and bare semiconductor dice.
Semiconductor components are becoming smaller and lighter. Chip scale packages (CSP), for example, have a peripheral outline that is slightly larger than that of an unpackaged die. A footprint for a typical chip scale package is only about 1.2 times the size of the die contained within the package. In addition, the weight of a typical chip scale package is about the same as an unpackaged die. Other types of semiconductor components, such as conventional plastic packages (e.g., TSOP, SOJ, LCC), BGA devices (e.g., xcexcBGA and FBGA devices), and xe2x80x9cstrip formxe2x80x9d devices are also becoming smaller and lighter. These smaller and lighter semiconductor components are more difficult to handle and transport during various processes such as testing, marking, packaging and assembly on circuit boards and electronic devices.
Typically, small semiconductor components are transported between various manufacturing and packaging operations in carriers. One type of carrier used widely in the industry includes a molded plastic frame having separate mounting sites for the components. These types of carriers are manufactured by different manufacturers such as Fluoroware of Minneapolis, Minn.
Typically, the frames for this type of carrier can be stacked for enclosing and protecting the components. In addition, the frames can have a xe2x80x9cstandardxe2x80x9d peripheral configuration, and xe2x80x9cstandardxe2x80x9d features that permit handling by standard equipment, such as magazines and conveyor tracks. The standard features can include lugs, recesses, chamfers and other features formed integrally with the frame. One type of standard carrier is constructed according to JEDEC (Joint Electron Device Engineering Council) standards, and is known as a JEDEC carrier.
On some types of carriers the components merely rest on the mounting sites and are restrained from movement only in the X and Y directions. The mounting sites, for example, can comprise molded tabs that engage the corners or sides of the components, or alternately pockets having peripheral outlines matching that of the components. Movement in the Z-direction is not restrained, so that the carrier must be maintained in an upright position to prevent the components from becoming dislodged from the mounting sites. Also to prevent dislodging of components, the process equipment for handling the carriers must be designed to minimize rough handling and movement of the carriers. In addition, personnel handling the carriers must be careful not to dislodge the components from the mounting sites during handling of the carriers.
Other types of carriers utilize a retention mechanism to physically engage and hold the component on the mounting site. These types of carriers are manufactured by Advantest of Japan and Aetrium of St. Paul, Minn. A representative retention mechanism includes spring loaded tabs that latch the edges of the component as it is held in a pocket. With these carriers, the frame can comprise molded plastic, or another electrically insulating material, such as ceramic or glass filled resin.
One problem with this type of carrier is that the retention mechanism complicates the design of the carrier, and requires the carrier to be larger, heavier and more expensive. In addition, specialized equipment is required to actuate and unactuate the retention mechanisms, and to load and unload the components from the mounting sites. Further, the components can be damaged due to misalignment during loading and unloading, and can also be damaged should they become dislodged. Bent leads, and deformed solder balls, are examples of damage that can occur to components due to misalignment or dislodging in a carrier.
Still another type of carrier includes a plastic frame and an elastomeric membrane formulated to provide a releasable adhesive surface. Sometimes rather than having separate mounting sites, the frame and elastomeric membrane can accommodate various components having different sizes and shapes. Representative elastomeric membrane materials include silicone, polyurethane, thermoplastic elastomers and polyimide. This type of carrier is manufactured by Vichem Corporation, of Sunnyvale, Calif. under the trademark xe2x80x9cGEL-PAKxe2x80x9d. Although the components are lightly restrained by the elastomeric material, this type of carrier is not suitable for some applications in which the components must be totally restrained in the Z-direction.
The present invention is directed to an improved carrier in which the components are retained by a low tack adhesive member on the component mounting sites. The carrier can be made smaller, lighter and cheaper than carriers having retention mechanisms, and does not require specialized handling equipment.
In accordance with the present invention, an improved carrier for semiconductor components is provided. Also provided are an improved semiconductor handling system employing the carrier, and an improved method for handling semiconductor components using the carrier.
The carrier, simply stated, comprises: a frame having a plurality of component mounting sites; and adhesive members formed on the component mounting sites for retaining the components on the carrier. The adhesive members are configured to exert a first adhesive force for retaining the components on the carrier, and a second adhesive force for bonding to the carrier.
In an illustrative embodiment, the adhesive members comprise pieces of polymer tape having an inner surface covered with a high tack adhesive layer, and an outer surface covered with a low tack adhesive layer. The high tack adhesive layers are formulated to provide semi permanent attachment of the polymer tape to the frame. The low tack adhesive layers are formulated to retain the components on the component mounting sites during normal handling of the carrier, but to allow removal of the components from the component mounting sites using conventional tools (e.g., pick and place vacuum tools).
The adhesive forces exerted by the adhesive members on the components are determined by the size of contact areas with the components, and by the adhesive qualities of the low tack adhesive layers. In a similar manner the adhesive forces exerted by the adhesive members on the frame are determined by the size of contact areas with the frame, and by the adhesive qualities of the high tack adhesive layers. Accordingly, the contact areas and adhesive qualities can be adjusted as required to achieve desired adhesive forces on the component and frame.
The polymer tape can comprise polyimide, polyethylene or polypropylene, on which the high tack adhesive layer, and the low tack adhesive layer can be formed using a suitable deposition process (e.g., spraying, printing, stenciling). The high tack adhesive layer can comprise a pressure activated adhesive, a heat activated adhesive, or a curable adhesive such as an epoxy, acrylic or silicone. The low tack adhesive can comprise a repositionable pressure sensitive adhesive.
In an alternate embodiment the adhesive members comprise a low tack adhesive layer that is sprayed, cast in place, or otherwise formed, on topographical features of the frame, such as indentations, ridges or serrations. The topographical features are configured to provide an increased surface area for adherence of the low tack adhesive layer to the frame. In another alternate embodiment the adhesive members comprise a low tack adhesive layer cast in place, or otherwise formed, on a priming layer formed on the frame. The priming layer is configured to increase the adhesion of the low tack adhesive layer to the frame.
In the illustrative embodiment the frame comprises molded plastic, and has a peripheral configuration and external features constructed according to standards of an industry standard setting body, such as JEDEC. Standardized equipment, such as magazines and conveyor tracks, can thus be used for transporting and handling the frame, with the components retained thereon. The frame also includes stacking ridges that permit stacking of multiple frames.
Preferably the component mounting sites are formed integrally with the frame using a molding process. The component mounting sites can be configured to retain a particular type of component, such as a semiconductor package, a chip scale package, a ball grid array device, an unpackaged semiconductor die, or a strip form device. The component mounting sites can comprise ridges, tabs, or pockets, which correspond in size to peripheral features of the components, such as terminal leads, edge surfaces, or end surfaces thereof. In addition, the component mounting sites can be configured to retain the components in a xe2x80x9clive bugxe2x80x9d position wherein the component leads are down, or in a xe2x80x9cdead bugxe2x80x9d position wherein the component leads are up.
The semiconductor handling system includes the carrier and a conventional pick and place vacuum tool. The vacuum tool is configured to exert a force on the components for removing the components from the adhesive members. The force exerted by the vacuum tool is greater than the adhesive force of the adhesive members on the components, but less than the adhesive force of the adhesive members on the carrier.
The method for handling semiconductor components includes the steps of: providing a carrier comprising a frame having an arrangement of component mounting sites; providing adhesive members on the component mounting sites comprising pieces of polymer tape having low tack adhesive surfaces for retaining the components and high tack adhesive surfaces for bonding to the frame; placing the components on the adhesive members; handling or transporting the components using the carrier, with the components retained on the adhesive members; and then removing the components from the component mounting sites using conventional vacuum tools.